Add cargo-deny to mach-tidy to check license compliance. (#32465)

* Use cargo-deny to check license compliance.

All licenses should be MPL-2.0 or weaker.

* Run cargo-deny check licenses in mach tidy

* fmt

* Fix inverted boolean

* Move cargo deny to tidy.py

* Add quotes around license in error message

* Integrate `cargo-deny` into tidy fully

* Fix script tests

---------

Co-authored-by: Martin Robinson <mrobinson@igalia.com>

python/servo/platform/base.py

@@ -59,6 +59,7 @@ class Base:
         if not skip_platform:
             installed_something |= self._platform_bootstrap(force)
         installed_something |= self.install_taplo(force)
+        installed_something |= self.install_cargo_deny(force)
         installed_something |= self.install_crown(force)
 
         if not installed_something:
@@ -74,6 +75,16 @@ class Base:
 
         return True
 
+    def install_cargo_deny(self, force: bool) -> bool:
+        if not force and shutil.which("cargo-deny") is not None:
+            return False
+
+        print(" * Installing cargo-deny...")
+        if subprocess.call(["cargo", "install", "cargo-deny", "--locked"]) != 0:
+            raise EnvironmentError("Installation of cargo-deny failed.")
+
+        return True
+
     def install_crown(self, force: bool) -> bool:
         print(" * Installing crown (the Servo linter)...")
         if subprocess.call(["cargo", "install", "--path", "support/crown"]) != 0:

python/servo/testing_commands.py

@@ -228,7 +228,7 @@ class MachCommands(CommandBase):
     def test_tidy(self, all_files, no_progress):
         tidy_failed = tidy.scan(not all_files, not no_progress)
 
-        print("\r ➤  Checking formatting of rust files...")
+        print("\r ➤  Checking formatting of Rust files...")
         rustfmt_failed = call(["cargo", "fmt", "--", *UNSTABLE_RUSTFMT_ARGUMENTS, "--check"])
         if rustfmt_failed:
             print("Run `./mach fmt` to fix the formatting")